Detailed Description

Namespace for the declaration of universal constants. Since the availability in math.h is not always guaranteed, we put them here. Since this file is included by base/config.h, they are available to the whole library.

The constants defined here are a subset of the M_XXX constants sometimes declared in the system include file math.h, but without the prefix M_.

In addition to that, we declare invalid_unsigned_int to be the largest unsigned integer representable; this value is widely used in the library as a marker for an invalid index, an invalid size of an array, and similar purposes.

Function Documentation

bool numbers::is_nan

(

const double

x

)

inline

Check whether a value is not a number.

This function uses either std::isnan, isnan, or _isnan, whichever is available on the system and returns the result.

If none of the functions detecting NaN is available, this function returns false.

Return true if the given value is a finite floating point number, i.e. is neither plus or minus infinity nor NaN (not a number).

Note that the argument type of this function is double. In other words, if you give a very large number of type long double, this function may return false even if the number is finite with respect to type long double.

Provide an object of type T filled with a signaling NaN that will cause an exception when used in a computation. The content of these objects is a "signaling NaN" ("NaN" stands for "not a number", and "signaling" implies that at least on platforms where this is supported, any arithmetic operation using them terminates the program). The purpose of such objects is to use them as markers for uninitialized objects and arrays that are required to be filled in other places, and to trigger an error when this later initialization does not happen before the first use.

Representation of the largest number that can be put into an unsigned integer. This value is widely used throughout the library as a marker for an invalid unsigned integer value, such as an invalid array index, an invalid array size, and the like.

Representation of the largest number that can be put into a size_type. This value is used throughout the library as a marker for an invalid size_type value, such as an invalid array index, an invalid array size, and the like. Invalid_size_type is equivalent to invalid_dof_index.

A boundary indicator number that we reserve for internal faces. We assume that all valid boundary_ids lie in the range [0, internal_face_boundary_id).

This is an indicator that is used internally (by the library) to differentiate between faces that lie at the boundary of the domain and faces that lie in the interior of the domain. You should never try to assign this boundary indicator to anything in user code.

The subdomain id assigned to a cell whose true subdomain id we don't know, for example because it resides on a different processor on a mesh that is kept distributed on many processors. Such cells are called "artificial".